1. Field of the Invention
The present invention relates to a stereo camera and, particularly, to a stereo camera which decreases losses in the right and left pictures.
2. Description of the Prior Art
In most of the conventional stereo cameras, the distance between the optical axes of the right and left photographing lenses has been set to be nearly the same as the distance between the centers of the right and left pictures. Therefore, the photographing ranges of the right and left pictures are brought into agreement with each other at an infinite point but become out of agreement as the photographing distance becomes shorter than an infinite point. Separate ranges (a-b) and (c-d) are photographed on the outer edge of the left picture of FIG. 22L and on the outer edge of the right picture of FIG. 22R, and the areas of the non-overlapped portions (a-b) and (c-d) become the greatest at the shortest photographing distance.
The non-overlapped portions of the stereo photography do not contribute to forming a stereo image when the films are viewed using a stereo slide viewer. When a stereo photograph taking a picture of a subject at a distance closer than an infinite point is mounted on a stereo slide mount for viewing the whole picture of the films, vertical lines appear at boundaries b and c between the overlapped portions and the non-overlapped portions where the edges of the other windows are overlapped when the stereo photography is viewed by both eyes impairing the interest. Usually, therefore, the non-overlapped portions of the films are masked by using a stereo slide mount having a width of windows narrower than the width of pictures of the films.
FIG. 24 shows a stereo slide mount 1 having a structure in which reversal films are sandwiched and held by a base frame 2 and a cover frame 3 having the same shape on a plane. The lateral width Ww of the left window 4L and the right window 4R is narrower than the width of pictures of the films to mask the non-overlapped portions formed on the pictures of the films at the shortest photographing distance. As shown, the films FL and FR photographing a subject at a short distance are mounted being offset outward relative to the windows 4L and 4R of the stereo slide mount 1 in order to mask the non-overlapped portions (a-b) and (c-d) shown in FIG. 23.
In the films which contain a subject at a distance and a subject in a close range, it is desired to correct the perspective feeling by adjusting the offset amount of the films in the lateral direction with respect to the windows of the stereo slide mount, so that the distance between the pictures of the subject (particularly, between the pictures of the subject in a close range) that most seriously affects the matching between the right and left pictures becomes equal to, or greater than, the distance Pw between the centers of the right and left windows of the stereo slide mount.
In the case of a stereo photography taking a picture of a subject at an infinite point, on the other hand, the photographing ranges of the pictures are nearly in agreement between the right film and the left film, and there is no need to mask the pictures. In practice, however, as shown in FIG. 25, both sides of the pictures of the right and left films FR, FL are masked by the windows 4R and 4L of the stereo slide mount, and the pictures are lost to a large extent.
In the past, there used to exist a stereo camera in which the distance between the optical axes of the right and left photographing lenses was narrowly set so that the photographing ranges of the right and left pictures were brought into agreement with each other at the shortest photographing distance contrary to the above-mentioned stereo camera. With this camera, however, non-overlapped portions are formed in which the photographing ranges are not brought into agreement on the insides of the right and left pictures when a subject at an infinite point is short contrary to the above-mentioned stereo camera. When a subject at an infinite point is shot, therefore, the non-overlapping portions of the inner sides must be masked by offsetting the right and left films toward the inside contrary to the films shown in FIG. 24. When a subject at the closest distance is shot, the mounting positions of the films need not be offset; i.e., the films are mounted in a state as shown in FIG. 25, and the pictures are lost in amounts same as that of the above-mentioned stereo camera.
In order to decrease the loss of the pictures, the present applicant has proposed a stereo camera in which the distance between the optical axes of the right photographing lens and the left photographing lens is automatically adjusted as well as a stereo camera in which the distance between the optical axes is manually adjusted. According to these stereo cameras of the type in which the distance between the optical axes is varied, the photographing ranges of the right and left pictures are brought into agreement over the whole photographing distances to suppress the occurrence of non-overlapped portions where the right and left pictures are not overlapped one upon the other. It is therefore allowed to decrease the loss of pictures by selecting the width of windows of the stereo slide mount to be nearly equal to the width of pictures of the films. However, provision of the mechanism for adjusting the distance between the optical axes causes the constitution of the stereo camera to become complex and inevitably drives up the cost.
Thus, there arouses a technical assignment that must be solved for decreasing the loss of pictures as much as possible in a stereo camera of a simple structure in which the distance between the optical axes is fixed. The object of the present invention is to solve the above-mentioned problem.